The 8051 is CISC based architecture.
It follows the Harvard architecture principles of memory interface,
so has separate program & data memory. 16 of the available 32 I/O lines
are used for accessing the external memory.
We can access a maximum of 64KB of program and
64 KB data memory externally. 8 of the IO lines are
used as both Address & data lines.

Both the program memory and data memories are 64K bytes. Program memory is read only and Data memory is readable/writable.
Program Store Enable is the read strobe signal used to access external program memory.
There are RD and WR signals used for reading from and writing to the external memory.

After reset signal is applied to the microcontroller ,
program execution starts from 0th location as stored in the program memory.

Microcontroller PSW (Program Status Word),BIT ADDRESSABLE

RS0 and RS1 selects register bank to use.
OV is Overflow Flag set by arithmetic operations.
P is the parity bit set by hardware, if it contains odd number of 1s, otherwise it is zero.
AC is the Auxiliary Carry Flag(from addition operation)
CY is the carry flag(from ALU operation)

Microcontroller PCON (Power Control Register),NOT BIT ADDRESSABLE

PD-Activates power down operation in microcontroller.
IDL- Activates idle mode operation in microcontroller.